he development of effective and efficient training methods of jumping ability attracts a large interest among coaches and athletes due to the importance of this skill in many different sports. The demands on the jumping performance of the athlete vary considerably between different sports. In certain individual sports such as high jump and high dive, jumping performance is a highly specialized closed skill. Most team sports such as volleyball and basketball, however, require a large and flexible repertoire of jumping skills related to different situations of the game. A volleyball player must sometimes get off the ground quickly in response to a visual cue rather than jump for maximal height and at other times he/she may have to rebound immediately after landing from a previous jump. The training process for vertical jumping should reflect the specific demands of both (1) the sport and (2) the individual athlete. The aim of this presentation is to gain further insight into the concept of specificity in the training process of vertical jumping and to see how it affects jumping performance in the individual athlete. A very common experience amongst coaches is that individuals respond very differently when exposed to the same training method. While some subjects show major increases in jumping height, others experience no change or even a decrease in performance. This is especially true for highly trained elite athletes with a long history of strength training. It is suggested that this is partly due to a gradually increased difficulty to maintain a high degree of specificity in the training process with increasing physical performance. To solve this problem we first must determine what factors limit the performance of a vertical jump. A practical approach would be to experimentally study good and bad jumpers and to correlate different aspects of their performance to factors that can be influenced by training. However, different subjects may differ on several factors simultaneously, so to provide a detailed insight into the mechanism by which certain factors influence jump height, the use of computerized forward dynamic simulations and optimization of constrained types of jumps seem indicated. This approach allows full control over all variables that influence jump height. Ideally, the outcome of an analysis of which factors are important and why they are important, will help us design a set of tests providing information to the coach about factors limiting the performance in each athlete. In this process both practical and theoretical knowledge is required suggesting that the scientist and practitioner should work closely together to solve these problems.